1. Field of the Invention
This invention relates in general to recovery units for recovering refrigerant from air conditioning systems, and in particular to a method for cleaning the air conditioning system of foreign matter.
2. Description of the Prior Art
Recovery units are used to recover refrigerant from air conditioning systems that require maintenance. A typical recovery unit has a compressor, condenser, evaporator, oil separator, and at least one filter. Hoses connect the air conditioning system to the recovery unit, with one hose connected to the suction side of the air conditioning system compressor, and the other hose connected to the high pressure or output side of the air conditioning compressor.
When operating, the recovery unit compressor draws refrigerant through the hoses, through the recovery unit expansion valve, evaporator, oil separator, filter and into the recovery unit compressor. The recovery unit compressor passes the high pressure, hot gas to the recovery unit condenser, which condenses the recovered refrigerant into a liquid, which then flows into a storage container. The filter in the recovery unit cleans the refrigerant as it passes through the recovery unit to the storage container.
The air conditioning system will often have foreign matter or debris contained within it due to its prior operation or due to a malfunction. It is desirable to clean the air conditioning system of the foreign matter as much as possible before recharging the air conditioning system.
Many maintenance workers disconnect the various components of the air conditioning system and discharge cleaning fluids through the various components individually in an effort to clean the components. While workable, this approach is time consuming.
Another prior art technique for cleaning a system is to provide the recovery unit with a liquid pump. The liquid pump supplies refrigerant liquid from the storage container to the air conditioning system. A hose connects the air conditioning system back to the recovery unit, so that the refrigerant will circulate through the air conditioning system. The flow rate provided by the liquid pump is preferably high enough to collect debris and purge the system, with the collected debris being trapped by the filters in the recovery unit. This technique requires an additional component, a liquid pump, along with associated valves and piping. Also, the liquid being pumped by the liquid pump through the conditioning system expands in the air conditioning system expansion valve into a gas, and consequently loses some of its ability to carry debris along with it.